Touchscreen with overlapping floating transparent conductive islands

ABSTRACT

Various configurations and arrangements for touchscreens are disclosed to accommodate for one or more optical discontinuities that can be present within these touchscreens. When the one or more optical discontinuities are present, these configurations and arrangements of the touchscreens present a single layer of transparent conductive material that can be difficult to perceive by a human eye when viewing the touchscreens. Additionally, various edge correction techniques are disclosed to adjust mutual capacitances along a perimeter of the touchscreens. These edge correction techniques adjust mutual capacitances such that the values of the mutual capacitances are substantially uniform throughout.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application to U.S. Nonprovisionalpatent application Ser. No. 16/942,107, with filed on Jul. 29, 2020,entitled Touchscreen Edge Correction, which is a continuationapplication to U.S. Nonprovisional patent application Ser. No.15/580,995, with 371(c) Date: Dec. 8, 2017, entitledProjected-Capacitive (PCAP) Touchscreen, which is a National Stage entryfrom PCT/US2017/042837 filed on Jul. 19, 2017, entitledProjected-Capacitive (PCAP) Touchscreen, which claims priority as acontinuation application to U.S. application Ser. No. 15/214,196 filedon Jul. 19, 2016, entitled Projected-Capacitive (PCAP) Touchscreen, allof which are incorporated herein by reference in their entireties.

BACKGROUND OF THE DISCLOSURE

A commercial electronic device interacts with an operator using atouchscreen. A touchscreen system, including a display and thetouchscreen, provides one or more images and/or video to the operatorand receives one or more commands and/or data from the operator. Thetouchscreen system detects a presence and/or a location of a touch froman operator, such as a finger of the operator, a hand of the operator,and/or other passive objects available to the operator, such as a stylusto provide an example, within the touchscreen. The commercial electronicdevices interpret the presence and/or the location of the touch as oneor more commands and/or data from the operator.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

Aspects of the present disclosure are best understood from the followingDetailed Description when read with the accompanying Drawings/Figures.It is noted that, in accordance with the standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features may be arbitrarily increased orreduced for clarity of discussion. In the drawings:

FIG. 1 illustrates a touch-interactive device according to an exemplaryembodiment of the present disclosure;

FIG. 2A and FIG. 2B illustrate an exemplary first electrode pattern thatcan be used to implement the touchscreen according to an exemplaryembodiment of the present disclosure;

FIG. 3A and FIG. 3B illustrate an exemplary second electrode patternthat can be used to implement the touchscreen according to an exemplaryembodiment of the present disclosure;

FIG. 4A through FIG. 4D illustrate a first exemplary touchscreenaccording to an exemplary embodiment of the present disclosure;

FIG. 5A through FIG. 5C illustrate a second exemplary touchscreenaccording to an exemplary embodiment of the present disclosure;

FIG. 6A through FIG. 6C illustrate a third exemplary touchscreenaccording to an exemplary embodiment of the present disclosure;

FIGS. 7A and 7B illustrate operation of the first exemplary touchscreenaccording to an exemplary embodiment of the present disclosure;

FIG. 8A through 8C conceptually illustrate example three-conductorsystems;

FIG. 9 illustrates in part a fourth exemplary touchscreen according toan exemplary embodiment of the present disclosure;

FIG. 10 illustrates in part a fifth exemplary touchscreen and itsoperation according to an exemplary embodiment of the presentdisclosure;

FIG. 11 illustrates a sixth exemplary touchscreen and its operationaccording to an exemplary embodiment of the present disclosure;

FIG. 12 illustrates a seventh exemplary touchscreen and its operationaccording to an exemplary embodiment of the present disclosure;

FIG. 13A through 13B illustrate an eighth exemplary touchscreenaccording to an exemplary embodiment of the present disclosure;

FIG. 14 is a flowchart of a first exemplary fabrication control flowthat can be used to fabricate the touchscreens according to an exemplaryembodiment of the present disclosure; and

FIG. 15 is a flowchart of a second exemplary fabrication control flowthat can be used to fabricate the touchscreens according to an exemplaryembodiment of the present disclosure.

The present disclosure will now be described with reference to theaccompanying drawings. In the drawings, like reference numbers generallyindicate identical, functionally similar, and/or structurally similarelements. The drawing in which an element first appears is indicated bythe leftmost digit(s) in the reference number.

DETAILED DESCRIPTION OF THE DISCLOSURE Overview

Various configurations and arrangements for touchscreens are disclosedto accommodate for one or more optical discontinuities that can bepresent within these touchscreens. When the one or more opticaldiscontinuities are present, these configurations and arrangements ofthe touchscreens approximately present a single layer of transparentconductive material that can be difficult to perceive by a human eye, asdesired, when viewing the touchscreens. In some situations, theseconfigurations and arrangements of the touchscreens present some areasof multiple layers of transparent conductive material and/or some areasof no transparent conductive material. However, the configurations andarrangements of the touchscreens sufficiently minimize these areas ofmultiple layers of transparent conductive material and/or these areas ofno transparent conductive material to be difficult to perceive by thehuman eye when viewing the touchscreen. Additionally, various edgecorrection techniques are disclosed to adjust mutual capacitances alonga perimeter of the touchscreens. These edge correction techniques adjustmutual capacitances such that local electrostatic fields generated bythe touchscreens result in values of mutual capacitance that aresubstantially uniform throughout.

A Touch-Interactive Device According to an Exemplary Embodiment of thePresent Disclosure

FIG. 1 illustrates a touch-interactive device according to an exemplaryembodiment of the present disclosure. As illustrated in FIG. 1, atouch-interactive device 100 represents a commercial electronic devicewith a large range of sizes and/or applications for communicatinginformation with an operator. For example, the touch-interactive device100 can represent a large commercial wall mounted device, having athirty-two inch diagonal dimension to provide an example, which can belocated in a large commercial retail store. Typically, commercialelectronic devices, when compared to consumer electronic devices, havelarger sizes and/or stationary locations. Additionally, commercialelectronic devices have a tendency to be manufactured in lowerquantities, such as tens of thousands of units, whereas consumerelectronic devices have a tendency to be manufactured in higherquantities, such as millions of units. As such, commercial electronicdevices typically are manufactured using a different process, such as ascreen printing process as opposed to a lithography process of theconsumer electronic devices, to lessen the overhead associated withmanufacturing the lower quantities. In an exemplary embodiment, thetouch-interactive device 100 can represent a point of sale system, akiosk system in retail and tourist settings, a video gaming device, anautomatic teller machine (ATM), or any other commercial electronicdevice having a touchscreen. Although the preferred embodiment describedherein represents a commercial electronic device manufactured in lowerquantities, those skilled in the relevant art(s) will recognize that theteachings herein may also be applicable to a consumer electronic devicemanufactured in higher quantities, e.g., an all-in-one computer, atablet computer, a smartphone, a personal digital assistant (PDA), asatellite navigation device, a video gaming device, an interne connectedappliance, or any other consumer electronic device.

Generally, the touch-interactive device 100 includes a touchscreen 102placed over a graphical display 104 and associated mechanical housingand/or electronics 106. Although not illustrated in FIG. 1, thetouch-interactive device 100 can be communicatively coupled to and/orcan include one or more peripheral devices such as a computer withnetworking capabilities, a speaker, a mouse, a graphic tablet, a barcodereader, a scanner, a microphone, a webcam, a game controller, a stylus,a digital camera, or any other suitable device that is capable ofconnecting to and/or interfacing with the touch-interactive device 100.As illustrated in FIG. 1, the touchscreen 102 is typically situated infront of the graphical display 104. The graphical display 104 operatesas an output device to provide one or more images and/or video relatingto one or more applications being executed by the touch-interactivedevice 100. In some situations, the operator of the touch-interactivedevice 100 can touch various areas of the touchscreen 102 thatcorrespond to various areas of the graphical display 104. Herein, atouch refers to physical contact between the touchscreen 102 and theoperator or the operator being sufficiently proximate to, with nophysical contact with, the touchscreen 102 to disrupt localelectrostatic fields within the touchscreen 102. The touchscreen 102detects a presence and/or a location of the touch and can interpret thepresence and/or the location of the touch as one or more commands and/ordata from the operator.

The touchscreen 102 includes a first set of electrodes and a second setof electrodes. In an exemplary embodiment, the first set of electrodesis oriented in a vertical direction, such as perpendicular to an x-axisof a Cartesian coordinate system, and the second set of electrodes isoriented in a horizontal direction, such as perpendicular to the y-axisof the Cartesian coordinate system. The first set of electrodes and thesecond set of electrodes, as presented with reference to FIG. 1, andthose referenced hereinbelow in alternate embodiments, can be formedusing indium-tin-oxide (ITO). However, those skilled in the relevantart(s) will recognize the first set of electrodes and/or the second setof electrodes can be formed using any suitable transparent conductivematerial without departing from the spirit and scope of the presentdisclosure. These suitable transparent conductive materials can includeone or more transparent conductive oxides (TCOs), one or more conductivepolymers, metal grids, one or more carbon nanotubes (CNT), graphene, oneor more nanowire meshes, and one or more ultra-thin metal films toprovide some examples.

The first set of electrodes and the second set of electrodes can beformed using a single-sided ITO (SITO) design or a double-sided ITO(DITO) design. In the SITO design, a first transparent substrateincludes a first ITO coating, which is selectively patterned to form thefirst set of electrodes, and a second transparent substrate includes asecond ITO coating, which is selectively patterned to form the secondset of electrodes. The first transparent substrate and the secondtransparent substrate having the first set of electrodes and the secondset of electrodes, respectively, are attached to each other with anoptically clear adhesive (OCA) to form the touchscreen 102 in the SITOdesign. However, in the DITO design, a first transparent substrateincludes a first ITO coating on a first surface and a second ITO coatingon a second surface, which are selectively patterned to form the firstset of electrodes and the second set of electrodes, respectively. Thefirst transparent substrate, having the first set of electrodes and thesecond set of electrodes, is attached to a second transparent substratewith the OCA to form the touchscreen 102 in the DITO design.

Ideally, the first set of electrodes is sufficiently proximate to thesecond set of electrodes such that no optical discontinuities arepresent when viewing the touchscreen 102. However, in some situations,the first set of electrodes is sufficiently separated from the secondset of electrodes to cause one or more optical discontinuities withinthe touchscreen 102 when viewing the touchscreen 102. The one or moreoptical discontinuities typically result from variances in contrast ofthe touchscreen 102 resulting from placement of the first set ofelectrodes and the second set of electrodes.

For example, when the first set of electrodes and the second set ofelectrodes are sufficiently close to each other, any separation betweenthe first set of electrodes and the second set of electrodes in thetouchscreen 102 can be difficult to perceive by a human eye when viewingthe touchscreen 102. In this example, the resolution of the human eye isinsufficient to visualize this separation. However, in another example,when the first set of electrodes and the second set of electrodes arenot sufficiently close to each other, any separation between the firstset of electrodes and the second set of electrodes in the touchscreen102 can be perceived by a human eye when viewing the touchscreen 102,since the resolution of the human eye can be sufficient to visualizethis separation.

In an exemplary embodiment, the touchscreen 102 can include one or morefloating transparent conductive islands between the first set ofelectrodes and the second set of electrodes to improve opticalperformance of the touchscreen 102. The one or more floating transparentconductive islands represent sections of conductive material that arenot electrically connected within the touchscreen 102, namely the one ormore floating transparent conductive islands are electrically floating.The one or more floating transparent conductive islands sufficientlyfill the gap of separation between the first set of electrodes and thesecond set of electrodes to make optical discontinuities difficult toperceive by a human eye when viewing the touchscreen 102.

As discussed above, the first transparent substrate and the secondtransparent substrate are selectively patterned to form the first set ofelectrodes, the second set of electrodes, and the one or more floatingtransparent conductive islands of the touchscreen 102. The first set ofelectrodes, the second set of electrodes, and the one or more floatingtransparent conductive islands form one or more electrode patterns. Thefirst transparent substrate and/or the second transparent substrate canbe selectively patterned using a lithography process, such asphotolithography to provide an example, and/or a screen printingprocess. The lithography process provides for a finer resolution thanthe screen printing process; however, overhead, such as equipment costs,mask design and setup, associated with the lithography process is muchgreater than the screen printing process. As such, the lithographyprocess is often implemented when large unit volumes of the touchscreen102 are to be fabricated, whereas the screen printing process is oftenimplemented when small unit volumes of the touchscreen 102 are to befabricated. Although embodiments of touchscreen fabrication aredescribed herein based on the screen printing process, this is meant asillustrative and not restrictive of the spirit and scope of the presentinvention, as is readily understood by those skilled in the art.

Exemplary Touchscreens that can be Implemented Within theTouch-Interactive Device According to an Exemplary Embodiment of thePresent Disclosure First Exemplary Touchscreen

FIG. 2A and FIG. 2B illustrate an exemplary first electrode pattern 200that can be used to implement the touchscreen according to an exemplaryembodiment of the present disclosure. Electrode pattern 200 includesvertical electrodes 202.1 through 202.k, configured and arranged inseries of k columns, and a plurality of adjacent floating transparentconductive islands disposed on a transparent substrate 204. Thetransparent substrate 204 represents one or more optically transparentmaterials. The one or more non-conductive, optically transparentmaterials can be flexible or inflexible. In an exemplary embodiment, thetransparent substrate 204 is implemented using a plate of glass.

The vertical electrodes 202.1 through 202.k are oriented in a verticaldirection, such as parallel to the y-axis of the Cartesian coordinatesystem and perpendicular to the x-axis of the Cartesian coordinatesystem. In this configuration and arrangement, the vertical electrodes202.1 through 202.k may be referred to as “X” electrodes due to theirrole in determining the x coordinates of the touch of the operator whenpresent. However, those skilled in the relevant art(s) will recognizethat the other configurations and arrangements for the verticalelectrodes 202.1 through 202.k are possible without departing from thespirit and scope of the present disclosure.

As illustrated in FIG. 2A, the vertical electrodes 202.1 through 202.kinclude electrode pads 206.1.1 through 206.i.k and electrode terminuses208.1.1 through 208.2.k. In an exemplary embodiment, the electrodeterminuses 208.1.1 through 208.2.k represent interfaces between theelectrode pads 206.1.1 through 206.i.k and associated electronics, suchas the associated mechanical housing and/or electronics 106 (FIG. 1),which can be electrically coupled to the associated electronics, such asby using one or more printed silver conductors on the transparentsubstrate 204 and/or one or more flex cables.

As additionally illustrated in FIG. 2A, the electrode pads 206.1.1through 206.i.k are configured and arranged in a series of i rows and aseries of k columns on the transparent substrate 204. Similarly, theelectrode terminuses 208.1.1 through 208.2.k are configured and arrangedin a series of two rows and a series of k columns on the transparentsubstrate 204. Suitable connections between the electrode pads 206.1.1through 206.i.k to corresponding electrode terminuses 208.1.1 through208.2.k form a corresponding vertical electrode from among the verticalelectrodes 202.1 through 202.k. For example, the electrode pads 206.1.1through 206.i.1 within a first column are mechanically and electricallyconnected to the electrode terminuses 208.1.1 through 208.2.1 from amonga first column to form the vertical electrode 202.1. However, thoseskilled in the relevant art(s) will recognize that other groupings ofthe electrode pads 206.1.1 through 206.i.k for one or more of thevertical electrodes 202.1 through 202.k are possible without departingfrom the spirit and scope of the present disclosure.

As shown in FIG. 2A, electrode pads 206.1.1 through 206.i.k can eachhave one or more floating transparent conductive islands adjacent to it.For example, each of electrode pads 206.1.1 through 206.i.k can havefour floating transparent conductive islands 212.1 through 212.aadjacent to it, as illustrated in further detail with respect toelectrode pad 206.1.k−1 located in a portion 210 of electrode pattern200. Although four floating transparent conductive islands 212.1 through212.a are illustrated in FIG. 2A, those skilled in the relevant art(s)will recognize that other numbers of transparent conductive islands arepossible without departing from the spirit and scope of the presentdisclosure. In an exemplary embodiment, the electrode pads 206.1.1through 206.i.k and the plurality of floating transparent conductiveislands can be implemented using a suitable transparent conductor, e.g.,indium-tin-oxide (ITO). Further, although the electrode pads 206.1.1through 206.i.k are implemented in a shape of a diamond in FIG. 2A, itshould be appreciated that this is illustrative and not restrictive ofthe shape that can be implemented by those skilled in the relevantart(s).

As the term ‘floating’ implies, the plurality of floating transparentconductive islands represent shapes of transparent conductive material,which are not electrically connected within the electrodes 202.1 through202.k. In an embodiment, the plurality of floating transparentconductive islands eliminate, or substantially reduce, one or moreoptical discontinuities that would be otherwise present in a touchscreenthat includes electrodes 202.1 through 202.k.

FIG. 2B illustrates a cross-section of the portion 210 of electrodepattern 200 along the line A-A′, and includes a cross-section of thetransparent substrate 204, a cross-section of the electrode pad206.1.k−1, a cross-section of the floating transparent conductive island212.1, and a cross-section of the floating transparent conductive island212.3. In an exemplary embodiment, the transparent substrate 204 isimplemented as a plate of glass with an approximate thickness between afraction of a millimeter to several millimeters, while the electrode pad206.1.k−1, the floating transparent conductive island 212.1, and/or thefloating transparent conductive islands 212.3 is implemented using acoating of ITO with an approximate thickness less than a wavelength oflight. The cross-section of the portion 210 of electrode pattern 200 isto be further described with reference to FIG. 4B and FIG. 4D.

FIG. 3A and FIG. 3B illustrate an exemplary second electrode pattern 300that can be used to implement the touchscreen according to an exemplaryembodiment of the present disclosure. Second electrode pattern 300includes horizontal electrodes 302.1 through 302.p, configured andarranged in a series of p rows, and a plurality of adjacent floatingtransparent conductive islands disposed on a transparent substrate 304.The transparent substrate 304 is substantially similar to thetransparent substrate 204 and will not be discussed in further detail.However, those skilled in the relevant art(s) will recognize that thetransparent substrate 304 can be implemented with a different materialfrom the transparent substrate 204 without departing from the spirit andscope of the present disclosure.

In the exemplary embodiment illustrated in FIG. 3A, the horizontalelectrodes 302.1 through 302.p are oriented in a horizontal direction,such as perpendicular to the y-axis of the Cartesian coordinate systemand parallel to the x-axis of the Cartesian coordinate system. In thisconfiguration and arrangement, the horizontal electrodes 302.1 through302.p may be referred to as “Y” electrodes due to their role indetermining the y coordinates of the touch of the operator when present.However, those skilled in the relevant art(s) will recognize that theother configurations and arrangements for the electrodes 302.1 through302.p are possible without departing from the spirit and scope of thepresent disclosure.

As illustrated in FIG. 3A, the horizontal electrodes 302.1 through 302.pinclude electrode pads 306.1.1 through 306.p.q and electrode terminuses308.1.1 through 308.p.2. In an exemplary embodiment, the electrodeterminuses 308.1.1 through 308.p.2 represent interfaces between theelectrode pads 306.1.1 through 306.p.q and associated electronics, suchas the associated mechanical housing and/or electronics 106 (FIG. 1),which can be electrically coupled to the associated electronics, such asby using one or more printed silver conductors on the transparentsubstrate 304 and/or one or more flex cables.

As additionally illustrated in FIG. 3A, the electrode pads 306.1.1through 306.p.q are configured and arranged in a series of p rows and aseries of q columns on the transparent substrate 304. Similarly, theelectrode terminuses 308.1.1 through 308.p.2 are configured and arrangedin a series of p rows and a series of two columns on the transparentsubstrate 304. Suitable connections between the electrode pads andcorresponding electrode terminuses form a corresponding horizontalelectrode. For example, the electrode pads 306.1.1 through 306.1.q aremechanically and electrically connected to the electrode terminuses308.1.1 through 308.1.2 to form the horizontal electrode 302.1. However,those skilled in the relevant art(s) will recognize that other groupingsof the electrode pads 306.1.1 through 306.p.q for one or more of thehorizontal electrodes 302.1 through 302.p are possible without departingfrom the spirit and scope of the present disclosure.

As shown in FIG. 3A, electrode pads 306.1.1 through 306.p.q, can eachhave one or more floating transparent conductive islands adjacent to it.For example, each of electrode pads 306.1.1 through 306.p.q can havefloating transparent conductive islands 312.1 through 312.a and floatingtransparent conductive islands 314 adjacent to it, as illustrated infurther detail with respect to electrode pad 306.2.q located in aportion 310 of electrode pattern 300. In an embodiment, the electrodepads 306.1.1 through 306.p.q and the plurality of floating transparentconductive islands of electrode pattern 300 are substantially similar tothe electrode pads 206.1.1 through 206.i.k and the plurality of floatingtransparent conductive islands of electrode pattern 200, respectively;therefore, only differences are discussed in further detail herein.

FIG. 3B illustrates a cross-section of the portion 310 of electrodepattern 300 along the line B-B′, which includes a cross-section of thetransparent substrate 304, a cross-section of the electrode pad 306.2.q,a cross-section of the floating transparent conductive island 312.1, anda cross-section of the floating transparent conductive island 312.3. Thecross-section of the portion 310 of electrode pattern 300 is to befurther described with reference to FIG. 4B and FIG. 4D.

FIG. 4A through FIG. 4D illustrate a first exemplary touchscreen 400according to an exemplary embodiment of the present disclosure. Asillustrated in FIG. 4A, the first electrode pattern 200, illustrated in“light gray,” and the second electrode pattern 300, illustrated in “darkgray,” are overlaid on top of each other to form the touchscreen 400. Inan embodiment, transparent substrates 204 and 304 are attached to eachother (with the electrode patterns 200 and 300 facing each other) withan optically clear adhesive (OCA) to form the touchscreen 400. Asillustrated in FIG. 4A, the vertical electrodes 202.1 through 202.k areplaced side-by-side in a horizontal direction where each successivevertical electrode 202.1 to 202.k has an increasing x coordinate in aCartesian coordinate system to provide an example. Similarly, thehorizontal electrodes 302.1 through 302.p are placed one-above-the-otherin a vertical direction where each successive horizontal electrode 302.1to 302.q has an increasing y coordinate in a Cartesian coordinate systemto provide an example, to form the touchscreen 400. In an exemplaryembodiment, the touchscreen 400 represents a projected capacitive (PCAP)touchscreen.

FIG. 4A additionally illustrates a portion of the touchscreen 400 infurther detail. As discussed above, the touchscreen 400 is formed byoverlaying electrode patterns 200 and 300 on top of each other. Ideally,when electrode patterns 200 and 300 are overlaid on top of each other, asingle layer of transparent conductive material can be perceived by thehuman eye when viewing the touchscreen 400. However, in some situations,one or more optical discontinuities may be present in the touchscreen400.

As illustrated in FIG. 4A, one or more first regions 402 represent oneor more first optical discontinuities having two or more layers oftransparent conductive material formed by the overlaying of electrodepatterns 200 and 300. For example, the one or more first regions 402result from connections among columns of the electrode pads 206.1.1through 206.i.k (of electrode pattern 200) overlaying correspondingconnections among rows of the electrode pads 306.1.1 through 306.p.q (ofelectrode pattern 300).

As further illustrated in FIG. 4A, one or more second regions 404 and406, illustrated in “white” in FIG. 4A, represent one or more secondoptical discontinuities having no layers of transparent conductivematerial formed by the overlaying of electrode patterns 200 and 300. Theone or more second regions 404 represent regions having no layers oftransparent conductive material at the ends of the floating transparentconductive islands 212.1 through 212.a (of electrode pattern 200) and/orthe floating transparent conductive islands 312.1 through 312.a (ofelectrode pattern 300). Similarly, the one or more second regions 406represent regions having no layers of transparent conductive materialbetween the electrode pads 206.1.1 through 206.i.k and the electrodepads 306.1.1 through 306.p.q and associated floating transparentconductive islands.

FIG. 4B illustrates a cross-section 420 of the portion of thetouchscreen 400 along the line C-C′, which includes a cross-section ofelectrode pattern 200, namely a cross-section of transparent substrate204, electrode pads 206.1.k−1 and 206.2.k, the floating transparentconductive islands 212.1 (adjacent to each of electrode pads 206.1.k−1and 206.2.k), and the floating transparent conductive islands 212.3(adjacent to each of electrode pads 206.1.k−1 and 206.2.k), and across-section of electrode pattern 300, namely, a cross-section of thetransparent substrate 304, electrode pad 306.3.q−1, electrode pad306.2.q, and electrode terminus 308.1.1, the floating transparentconductive islands 312.1 (adjacent to electrode pads 306.3.q−1 and306.2.q), and the floating transparent conductive islands 312.3(adjacent to electrode pad 306.2.q and electrode terminus 308.1.2).Transparent substrates 204 and 304 are attached using an optically clearadhesive (OCA) 408 to form the touchscreen 400. As referenced throughoutherein, OCA can be an acrylic-based adhesive, a silicone-based adhesive,polyvinyl butyral (PVB), ethylene-vinyl acetate (EVA), or any othersuitable OCA that will be recognized by those skilled in the relevantart(s).

As illustrated in FIG. 4B, electrode patterns 200 and 300 are overlaidon top of each other in such a manner that there is little to no overlapand little to no horizontal separation between electrode pads 206.2.k−1and 206.1.k, the floating transparent conductive islands 212.1, and/orthe floating transparent conductive islands 212.3 of electrode pattern200 and electrode pads 306.3.q−1 and 306.2.q, electrode terminus308.1.2, the floating transparent conductive islands 312.1, and/or thefloating transparent conductive islands 312.3 of second electrodepattern 300. As such, the cross-section of the portion of thetouchscreen 400 can be perceived by the human eye as having acontinuous, single layer of transparent conductive material when viewedfrom above in a normal direction 410 that is perpendicular, orapproximately perpendicular, to the cross-section of the portion of thetouchscreen 400.

In an embodiment, the boundary alignment illustrated in FIG. 4B betweenrespective elements of electrode pattern 200 and electrode pattern 300(i.e., no or minimal overlap and no or minimal horizontal separation orgap) is achieved in accordance with an etch resolution of thefabrication process used to create electrode patterns 200 and 300. Forexample, in the case of fabrication using a screen printing process, dueto the screen printing process for depositing etchant, and the etchingprocess itself, there is a minimum separation between an electrode padand an associated floating island below which electrical separation isnot assured. As a typical touchscreen contains thousands of floatingislands, reliable electrical separation at a high statistical level isdesired. This minimum separation is denoted herein as the “etchresolution” of the fabrication process. A representative value of etchresolution is 200 microns, or more generally in a range from 100 to 300microns. The resolution of the screen printing process for depositingetchant on a ITO coated glass contributes to the etch resolution as doesbleeding or spreading of the etchant during the etch reaction itself.

However in some situations, the cross-section of the portion of thetouchscreen 400 can be perceived by the human eye as not being thesingle layer of transparent conductive material when viewed from abovein an angular direction 412 that is offset from the normal direction410. For example, some portions of the cross-section of the portion ofthe touchscreen 400 can be perceived as including no layers of thetransparent conductive material and/or two layers of the transparentconductive when viewed from above in the angular direction 412 causingone or more optical discontinuities within the cross-section of theportion of the touchscreen 400. Ideally, these one or more opticaldiscontinuities can be difficult to perceive by a human eye when viewingthe cross-section of the portion of the touchscreen 400. However, insome situations, the one or more optical discontinuities can beperceived by the human eye when viewing the cross-section of the portionof the touchscreen 400 in the angular direction 412.

For example, the single layer of transparent conductive material may notbe present in the cross-section of the portion of the touchscreen 400when viewed from above in the angular direction 412 that is offset fromthe normal direction 410, and/or the transparent substrate 204 may behorizontally shifted relative to the transparent substrate 304 when thetransparent substrate 204 and the transparent substrate 304 are attachedto form the touchscreen 400. In this example, conventional ray-tracinganalysis would lead those skilled in the relevant art(s) to expect thatsome portions of the cross-section of the portion of the touchscreen 400can be perceived as including no layers of the transparent conductivematerial and/or two layers of the transparent conductive material whenviewed from above in the angular direction 412 causing one or moreoptical discontinuities within the touchscreen 400. However, it has beendiscovered experimentally through perception tests that these one ormore optical discontinuities within the touchscreen 400 are notnecessarily perceived by the human eye when viewing the cross-section ofthe portion of the touchscreen 400 in the angular direction 412.Although these one or more optical discontinuities are present in thetouchscreen 400, one or more factors, such as a resolution of the humaneye at a viewing distance typical of commercial touchscreenapplications, a width range of floating transparent conductive islands212.1 through 212.a and floating transparent conductive islands 312.1through 312.a based on the capabilities of the screen printingprocesses, and/or a thickness of optically clear adhesive (OCA) 408separating the first electrode pattern 200 and the second electrodepattern 300 to provide some examples, can cause these one or moreoptical discontinuities to be difficult to be perceived by the human eyewhen viewing the touchscreen 400 from above in the angular direction412. Specifically, the inventors of the present disclosure havediscovered that this is the case when the resolution of the human eye isapproximately 200 microns, which corresponds to a viewing distance ofcommercial electronic devices, when the width of range of the floatingtransparent conductive islands 212.1 through 212.a, the floatingtransparent conductive islands 312.1 through 312.a, and/or correspondinggaps are approximately 200 microns or larger, which corresponds to thecapabilities of the screen printing processes, and/or when the thicknessof the optically clear adhesive (OCA) 408 separating the first electrodepattern 200 and the second electrode pattern 300 is approximately 200microns.

The exemplary embodiment as illustrated in FIG. 4A and FIG. 4B is ofparticular interest in the design of PCAP touchscreens that aremanufactured using the screen printing processes. In particular, thisexemplary embodiment accounts for both electronic and opticalperformance.

For example, a typical center-to-center spacing between the verticalelectrodes 202.1 through 202.k and the horizontal electrodes 302.1through 302.p is related to a size of the human finger, and thus, isbetween approximately 5 mm and approximately 7 mm to ensure that a touchfrom the operator overlaps multiple vertical electrodes 202.1 through202.k and/or multiple horizontal electrodes 302.1 through 302.p toprovide for efficient determination of a location of the touch withoutunnecessarily increasing the total number of electronics and hencechannels of electronics.

Further, a typical width of the floating transparent islands 212.1through 212.a and/or the floating transparent conductive islands 312.1through 312.a can be a factor of ten or more less than thecenter-to-center spacing between the vertical electrodes 202.1 through202.k and the horizontal electrodes 302.1 through 302.p, e.g.,approximately 250 microns; however, the width of floating transparentislands 212.1 through 212.a and/or the floating transparent conductiveislands 312.1 through 312.a can range from approximately 200 microns toapproximately 500 microns or beyond. This typical width and width rangealso apply to the width of gaps between an electrode pad 206 andfloating transparent conductive islands 212.1 through 212.a, as well asbetween an electrode pad 306 and floating transparent conductive islands312.1 through 312.a. It is of significance to note that while gapsbetween approximately 200 microns and approximately 500 micron can bereliably fabricated by the screen printing process, gaps significantlynarrower than 200 microns are problematic with the screen printingprocess. Thus, the exemplary embodiment as illustrated in FIG. 4A andFIG. 4B can provide designs for the touchscreen 400 that are compatiblewith the screen printing processes.

FIG. 4C illustrates a comparison of the cross-section 420 of the portionof the touchscreen 400 along the line C-C′ with cross-sections 414, 416,418 of conventional touchscreens. Referring to the cross-section 414,the simplest conventional design which is compatible with ITO patterningwith the screen printing process is represented, and includes ITOmaterial 422 and ITO material 424 that are selectively patterned onto afirst plate of glass 426 and a second plate of glass 428, respectively.The configuration and arrangement of the ITO material 422 and the ITOmaterial 424 provides a single, approximately substantially uniform,layer of the ITO for the cross-section 414 when viewed in a normaldirection, such as the normal direction 410 to provide an example, thatis perpendicular, or approximately perpendicular, to the cross-section414. Although this configuration and arrangement of the cross-section414 can satisfy optical and manufacturability goals for thisconventional touchscreen, this configuration and arrangement of thecross-section can lead to diminished electronic performance. A keyelectronic figure of merit, which is to be discussed in further detailbelow with reference to FIGS. 7A and 7B, is the touch-sensitivity ratioΔC_(M)/C_(M), which typically is desired to be large to aid touchdetection operation. Because edges of ITO material 422 and the ITOmaterial 424 are in close proximity in this arrangement, there is arelatively large contribution to the mutual capacitance, C_(M), which isminimally affected by a relatively remote touch of the operator on asurface of the first plate of glass 426, that is, for which thecorresponding contribution to ΔC_(M) is small.

Turning to the cross-section 416 of a second conventional touchscreen,ITO material 430 and ITO material 432 are included and selectivelypatterned onto the first plate of glass 426 and the second plate ofglass 428, respectively. The cross-section 416 is a much better designthan the cross-section 414 in terms of electronic performance, since itprovides a much better value for the touch-sensitivity ratioΔC_(M)/C_(M) when compared to the cross-section 414. However, thisincreased electronic performance leads to relatively large gaps, forexample approximately 500 microns, between the ITO material 430 and theITO material 432 which diminishes optical performance, since they aresufficiently large to be perceived by a human eye when viewing thecross-section 416 in the normal direction.

As further illustrated in FIG. 4C, the cross-section 418 of a thirdconventional touchscreen includes ITO material 434 and ITO islands 436and ITO material 438 that are selectively patterned onto the first plateof glass 426 and the second plate of glass 428, respectively. Thecross-section 418 alleviates the diminished optical performance of thecross-section 416 with the inclusion of the ITO islands 436. Gapsbetween the ITO material 434 and the ITO islands 436 are very narrow,such as 50 microns or less, so as to be difficult to be perceived by ahuman eye when viewing the cross-section 418. These gaps aresufficiently small that a lithography process, as opposed to a screenprinting process, is needed to be used, since the screen-printingprocess does not have the necessary resolution to print gaps of thesesizes. For consumer electronic devices, which have a tendency to bemanufactured in higher quantities, such as millions of units, thelithography process is often utilized. But, overhead associated with thelithography process can prevent the lithography process from being usedin manufacturing lower quantities, such as those of commercialelectronic devices. In these situations, the screen printing process ispreferred. None of the cross-sections 414, 416, and 418 representcross-sections of portions of conventional touchscreens that provide adesign with both optical and electronic performance and compatibilitywith screen printing manufacturing processes as does the touchscreen 400as described with reference to FIG. 4A, FIG. 4B, and FIG. 4D.

Referring now to FIG. 4D, an alternate cross-section of the portion ofthe touchscreen 400 along the line C-C′ according to an embodiment isillustrated. The alternate embodiment illustrated in FIG. 4D may besuitable in situations where the one or more optical discontinuities,discussed with reference to FIG. 4B above, can be perceived by the humaneye when viewing the cross-section of the portion of the touchscreen 400in the angular direction 412. Such parallax effects may occur and can bestronger, for example, when there is a greater distance between thefirst electrode pattern 200 and the second electrode pattern 300.Alternatively or additionally, if the touchscreen 400 and its associateddisplay are smaller in size, the human eye is likely to view thetouchscreen 400 and its associated display from a shorter distance andhence have a higher resolution in terms of microns of distance withinthe ITO electrode patterns. Also, some applications may demand a widerrange of viewing angles.

In the alternate embodiment of FIG. 4D, the floating transparentconductive islands 212.1, and/or the floating transparent conductiveislands 212.3 of the first electrode pattern 200 can be extended tooverlap electrode pads 306.3.q−1 and 306.2.q, electrode terminus308.1.2, the floating transparent conductive islands 312.1, and/or thefloating transparent conductive islands 312.3 of the second electrodepattern 300 Additionally, the floating transparent conductive islands312.1, and/or the floating transparent conductive islands 312.3 of thesecond electrode pattern 300 can be extended to overlap electrode pads206.2.k−1 and 206.1.k, the floating transparent conductive islands212.1, and/or the floating transparent conductive islands 212.3 of thefirst electrode pattern 200. As such, the cross-section of the portionof the touchscreen 400 can be perceived by the human eye as not havingany high-contrast discontinuities between regions with no layers oftransparent conductive material and two or one layers of the transparentconductive material when viewed from above in the angular direction 412.

Second Exemplary Touchscreen

FIG. 5A through FIG. 5C illustrate a second exemplary touchscreenaccording to an exemplary embodiment of the present disclosure. Asillustrated in FIG. 5A, a first electrode pattern 500 includes verticalelectrodes 502.1 through 502.k that are configured and arranged in aseries of k columns on the transparent substrate 204 and are oriented ina vertical direction, such as perpendicular to the x-axis of theCartesian coordinate system. The vertical electrodes 502.1 through 502.kinclude electrode pads 504.1.1 through 504.i.k and electrode terminuses506.1.1 through 506.2.k. The vertical electrodes 502.1 through 502.k aresubstantially similar to the vertical electrodes 202.1 through 202.k. Assuch, the electrode pads 504.1.1 through 504.i.k and electrodeterminuses 506.1.1 through 506.2.k are substantially similar to theelectrode pads 206.1.1 through 206.i.k and electrode terminuses 208.1.1through 208.2.k, respectively. Therefore, only differences between theseelectrodes, electrode pads, and electrode terminuses are to be discussedin further detail. In addition, electrode pattern 500 may include aplurality of floating transparent conductive islands adjacent to each ofelectrode pads 504.1.1 through 504.i.k and electrode terminuses 506.1.1through 506.2.k.

To illustrate the differences between these electrodes, electrode pads,and electrode terminuses, an electrode pad 504.m from among theelectrode pads 504.1.1 through 504.i.k is illustrated in further detailin FIG. 5A. As shown, electrode pad 504.m has four adjacent floatingtransparent conductive islands, disposed in a similar fashion asfloating islands 212.1 through 212.a described above. Further, one ormore floating transparent conductive islands 508 may be disposedadjacent to electrode pad 504.m. The one or more floating transparentconductive islands 508 are substantially similar to the one or morefloating transparent conductive islands 314 as described in FIG. 3A and3B except the one or more floating transparent conductive islands 508are on the transparent substrate 204 with the vertical electrodes 502.1through 502.k rather than on the transparent substrate 304 with thehorizontal electrodes 302.1 through 302.p, and are slightly taller inthe vertical direction.

As illustrated in FIG. 5B, a second electrode pattern 510 includeshorizontal electrodes 512.1 through 512.p that are configured andarranged in a series of p rows on the transparent substrate 304 orientedin a horizontal direction, such as perpendicular to the y-axis of theCartesian coordinate system. The horizontal electrodes 512.1 through512.p include electrode pads 514.1.1 through 514.p.q and electrodeterminuses 516.1.1 through 516.p.2, and are substantially similar to thehorizontal electrodes 302.1 through 302.p. As such, the electrode pads514.1.1 through 514.p.q and electrode terminuses 516.1.1 through 516.p.2are substantially similar to the electrode pads 306.1.1 through 306.p.qand the electrode terminuses 308.1.1 through 308.p.2, respectively.Therefore, only differences between these electrodes, electrode pads,and electrode terminuses are to be discussed in further detail. Inaddition, electrode pattern 510 may include a plurality of floatingtransparent conductive islands adjacent to each of electrode pads514.1.1 through 514.p.q and electrode terminuses 516.1.1 through516.p.2.

To illustrate the differences between these electrodes, electrode pads,and electrode terminuses, a region of the second electrode pattern 510is illustrated in further detail in FIG. 5B. As illustrated in FIG. 5B,floating transparent conductive islands, such as the floatingtransparent conductive islands 312.1 through 312.a illustrated in FIG.3, between adjacent electrode pads in each column of the series of qcolumns of the electrode pads 514.1.1 through 514.p.q are connected withthe same or optically similar materials to form one or more floatingtransparent conductive islands 518. For example, the floatingtransparent conductive islands 312.2 and 312.3 of the electrode pad514.1.q are connected to the floating transparent conductive islands312.1 and 312.a of the electrode pad 514.2.q as illustrated in theregion of the second electrode pattern 510 in FIG. 5B. The connectionsbetween floating transparent conductive islands 312.2 and 312.1 andbetween floating transparent conductive islands 312.3 and 312.a serve nobeneficial electronic purpose, and are provided to reduce the size ofregions with no layers of ITO relative to region 406 of touchscreen 400.Also, as the ends of the floating islands tend to be locations of maskemulsion wear, the second electrode pattern 510 in FIG. 5B has theadditional advantage of increasing mask durability by reducing thenumber of floating island ends.

As illustrated in FIG. 5C, the first electrode pattern 500, illustratedin “light gray,” and the second electrode pattern 510, illustrated in“dark gray,” are overlaid on top of each other and attached with anoptically clear adhesive (OCA) to form the touchscreen 520. As furtherillustrated in FIG. 5C, the vertical electrodes 502.1 through 502.k areplaced side-by-side in a horizontal direction where each successivevertical electrode 502.1 through 502.k has an increasing x coordinate ina Cartesian coordinate system to provide an example. Similarly, thehorizontal electrodes 512.1 through 512.p are placed one-above-the-otherin a vertical direction where each successive horizontal electrode 512.1through 512.p has an increasing y coordinate in a Cartesian coordinatesystem to provide an example, to form the touchscreen 520. In anexemplary embodiment, the touchscreen 520 represents a projectedcapacitive (PCAP) touchscreen. The touchscreen 520 is substantiallysimilar to the touchscreen 400. As such, the first electrode pattern 500and the second electrode pattern 510 are substantially similar to thefirst electrode pattern 200 and the second electrode pattern 300,respectively. Therefore, only differences between these first electrodepatterns and second electrode patterns are to be discussed in furtherdetail.

To illustrate the differences between these first electrode patterns andthese second electrode patterns, a region of the touchscreen 520 isillustrated in further detail in FIG. 5C, where the one or more regions522, illustrated in “white”, represent one or more opticaldiscontinuities having no layers of transparent conductive materialformed by the overlaying of the vertical electrodes 502.1 through 502.kand the horizontal electrodes 512.1 through 512.p as well as associatedtransparent conductive islands. In some situations, the one or moreregions 522 are smaller than the one or more second regions 406 asdiscussed in FIG. 4A, which cause the one or more regions 522 to be moredifficult to perceive by the human eye when viewing the touchscreen 520.Referring back to the one or more second regions 406 as illustrated inFIG. 4A, the one or more floating transparent conductive islands 518 asillustrated in FIG. 5C effectively overlap vertical sides of the one ormore second regions 406. This overlapping of the vertical sides cancause the one or more regions 522 to be smaller than the one or moresecond regions 406. Furthermore, as transparent floating conductiveisland 508 has been moved to the opposite ITO layer relative totransparent floating conductive island 314 of touchscreen 400, it can beexpanded vertically, reducing white area, without electricallyconnecting horizontal electrodes 512.1 through 512.p.

Third Exemplary Touchscreen

FIG. 6A through FIG. 6C illustrate a third exemplary touchscreenaccording to an exemplary embodiment of the present disclosure. Asillustrated in FIG. 6A, a first electrode pattern 600 includes verticalelectrodes 602.1 through 602.k that are configured and arranged in aseries of k columns on the transparent substrate 204. In the exemplaryembodiment illustrated in FIG. 6A, the vertical electrodes 602.1 through602.k are oriented in a vertical direction, such as perpendicular to thex-axis of the Cartesian coordinate system. The vertical electrodes 602.1through 602.k include electrode pads 604.1.1 through 604.i.k andelectrode terminuses 606.1.1 through 606.2.k. The vertical electrodes602.1 through 602.k are substantially similar to the vertical electrodes202.1 through 202.k. As such, the electrode pads 604.1.1 through 604.i.kand electrode terminuses 606.1.1 through 606.2.k are substantiallysimilar to the electrode pads 206.1.1 through 206.i.k and electrodeterminuses 208.1.1 through 208.2.k, respectively. Therefore, onlydifferences between these electrodes, electrode pads, and electrodeterminuses are to be discussed in further detail. In addition, electrodepattern 600 may include a plurality of floating transparent conductiveislands adjacent to each of electrode pads 604.1.1 through 604.i.k andelectrode terminuses 606.1.1 through 606.2.k.

To illustrate the differences between these electrodes, electrode pads,and electrode terminuses, an electrode pad 604.m from among theelectrode pads 604.1.1 through 604.i.k is illustrated in further detailin FIG. 6A. As shown, electrode pad 604.m has four adjacent floatingtransparent conductive islands 610.1 through 610.a, disposed in asimilar fashion as floating islands 212.1 through 212.a described above.By comparing the floating transparent conductive islands 212.1 through212.a and the floating transparent conductive islands 610.1 through610.a, those skilled in the relevant art(s) will recognize the floatingtransparent conductive islands 610.1 through 610.a are of sufficientlength to eliminate the need for the one or more floating transparentconductive islands 314 as described with reference to FIG. 3A and FIG.3B and/or the one or more floating transparent conductive islands 508 asdescribed with reference to FIG. 5A and FIG. 5C. In some situations, itis desirable to fully minimize stray capacitive coupling betweenneighboring electrodes, such as between the vertical electrode 602.1 andthe vertical electrode 602.2 and/or between the vertical electrode602.k−1 and the vertical electrode 602.k. In this respect, the firstarray electrodes 600 has the disadvantage of bringing the transparentconductors 608 of neighboring electrodes into close proximity and henceincreasing the capacitance between neighboring electrodes. In thesesituations, the first electrode pattern 200 as described in FIG. 2A andFIG. 2B is preferred.

As illustrated in FIG. 6B, a second electrode pattern 612 includeshorizontal electrodes 614.1 through 614.p that are configured andarranged in a series of p rows on the transparent substrate 304. In theexemplary embodiment illustrated in FIG. 6B, the horizontal electrodes614.1 through 614.p are oriented in a horizontal direction, such asperpendicular to the y-axis of the Cartesian coordinate The horizontalelectrodes 614.1 through 614.p include electrode pads 616.1.1 through616.p.q and electrode terminuses 618.1.1 through 618.p.2. The horizontalelectrodes 614.1 through 614.p are substantially similar to thehorizontal electrodes 302.1 through 302.p. As such, the electrode pads616.1.1 through 616.p.q and electrode terminuses 618.1.1 through 618.p.2are substantially similar to the electrode pads 306.1.1 through 306.p.qand electrode terminuses 308.1.1 through 308.p.2, respectively.Therefore, only differences between these electrodes, electrode pads,and electrode terminuses are to be discussed in further detail. Inaddition, electrode pattern 612 may include a plurality of floatingtransparent conductive islands adjacent to each of electrode pads616.1.1 through 616.p.q and electrode terminuses 618.1.1 through618.p.2.

To illustrate the differences between these electrodes, electrode pads,and electrode terminuses, an electrode pad 616.m from among theelectrode pads 616.1.1 through 616.p.q is illustrated in further detailin FIG. 6B. As shown, electrode pad 616.m has four adjacent floatingtransparent conductive islands 622.1 through 622.a, disposed in asimilar fashion as floating islands 212.1 through 212.a described above.By comparing the floating transparent conductive islands 312.1 through312.a and the floating transparent conductive islands 622.1 through622.a, those skilled in the relevant art(s) will recognize the floatingtransparent conductive islands 622.1 through 622.a are of sufficientlength to eliminate the need for the one or more floating transparentconductive islands 314 as described with reference to FIG. 3A and FIG.3B and/or the one or more floating transparent conductive islands 508 asdescribed with reference to FIG. 5A and FIG. 5C. In some situations, itis desirable to fully minimize stray capacitive coupling betweenneighboring electrodes, such as between the horizontal electrode 614.1and the horizontal electrode 614.2 and/or between the horizontalelectrode 614.(p−1) and the horizontal electrode 614.p. In this respect,the second electrode pattern 612 has the disadvantage of bringingtransparent conductors 608 of neighboring electrodes into closeproximity and hence increasing the capacitance between neighboringelectrodes. In these situations, the second electrode pattern 300 asdescribed in FIG. 3A and FIG. 3B is preferred.

As illustrated in FIG. 6C, the first electrode pattern 600, illustratedin “light gray,” and the second electrode pattern 612, illustrated in“dark gray,” are overlaid on top of each other and attached to eachother with an optically clear adhesive (OCA) to form the touchscreen622. As illustrated in FIG. 6C the vertical electrodes 602.1 through602.k are placed side-by-side in a horizontal direction where eachsuccessive vertical electrode 602.1 through 602.k has an increasing xcoordinate in a Cartesian coordinate system to provide an example.Similarly, the horizontal electrodes 614.1 through 614.p are placedone-above-the-other in a vertical direction where each successivehorizontal electrode 614.1 through 614.p has an increasing y coordinatein a Cartesian coordinate system to provide an example, to form thetouchscreen 622. The touchscreen 622 is substantially similar to thetouchscreen 400. As such, the first electrode pattern 600 and the secondelectrode pattern 612 are substantially similar to the first electrodepattern 200 and the second electrode pattern 300, respectively.Therefore, only differences between these first electrode patterns andsecond electrode patterns are to be discussed in further detail.

To illustrate the differences between these first electrode patterns andthese second electrode patterns, a region of the touchscreen 622 isillustrated in further detail in FIG. 6C. One or more regions 624,illustrated in “white” in FIG. 6C, represent one or more opticaldiscontinuities having no layers of transparent conductive materialformed by the overlaying of the vertical electrodes 602.1 through 602.kand the horizontal electrodes 614.1 through 614.p and associatedtransparent conductive floating islands. In some situations, the one ormore regions 624 are smaller than the one or more second regions 406 asdiscussed in FIG. 4A, which cause the one or more regions 624 to be moredifficult to perceive by the human eye when viewing the touchscreen 622.

Operation of the First Exemplary Touchscreen Through the Third ExemplaryTouchscreen

FIGS. 7A and 7B illustrate operation of the first exemplary touchscreenaccording to an exemplary embodiment of the present disclosure. Asdiscussed above in FIG. 4A, the first electrode pattern 200, illustratedin “light gray,” and the second electrode pattern 300, illustrated in“dark gray,” are attached to form the touchscreen 400. Although only theoperation of the touchscreen 400 is to be described in FIGS. 7A and 7B,those skilled in the relevant art(s) will recognize that this exemplaryoperation of the touchscreen 400 is likewise applicable to thetouchscreen 520 and/or the touchscreen 622 without departing from thespirit and scope of the present disclosure.

The touchscreen 400 can operate in a row scanning mode of operation orin a column scanning mode of operation. In the row scanning mode ofoperation, one or more horizontal electrodes from among the horizontalelectrodes 302.1 through 302.p are sequentially excited by a drivesignal. The drive signal capacitively couples to one or more verticalelectrodes from among the vertical electrodes 202.1 through 202.k.Transferred electrical charges or currents due to mutual capacitance(s)between the driven horizontal electrode and the one or more verticalelectrodes are measured to detect a presence and/or a location of atouch from an operator, such as a finger of the operator, a hand of theoperator, and/or other objects available to the operator, such as astylus to provide an example. Similarly, in the column scanning mode ofoperation, one or more vertical electrodes from among the verticalelectrodes 202.1 through 202.k are sequentially excited by a drivesignal. The drive signal capacitively couples to one or more horizontalelectrodes from among the horizontal electrodes 302.1 through 302.p.Transferred electrical charges or currents due to mutual capacitance(s)between the driven vertical electrode and the one or more horizontalelectrodes are measured to detect a presence and/or a location of atouch from an operator. The description to follow further describes theoperation of the touchscreen 400 in the row scanning mode of operation.Those skilled in the relevant art(s) will recognize that the columnscanning mode of operation operates in a similar manner withoutdeparting from the spirit and scope of the present disclosure.

During the row scanning mode of operation and as further illustrated inFIGS. 7A and 7B, a horizontal electrode from among the horizontalelectrodes 302.1 through 302.p is driven by an excitation signal whichcapacitively couples to all vertical electrodes 202.1 through 202.k.Specifically, FIG. 7A illustrates capacitive coupling of the drivesignal from horizontal electrode 302.2 and vertical electrode 202.k−1while FIG. 7B illustrates capacitive coupling of the drive signal fromhorizontal electrode 302.2 and vertical electrode 202.k. Generally, amutual capacitance “C_(M)” is associated with each of the horizontalelectrodes 302.1 through 302.p and a corresponding one of the verticalelectrodes 202.1 through 202.k. For example, if “r” represents an indexfor a vertical electrode 202.r from among the vertical electrodes 202.1through 202.k, and if “s” represents an index of a horizontal electrode302.s from among the horizontal electrodes 302.1 through 302.p, then k·pmutual capacitances are present between the vertical electrodes 202.1through 202.k and the horizontal electrodes 302.1 through 302.p, whichcan be denoted as the set of mutual capacitances C_(M)(r,s) for r=1 to kand s=1 to p.

Associated electronics, such as the associated mechanical housing and/orelectronics 106 to provide an example, electrically connected to thevertical electrodes 202.1 through 202.k measures (via received currentor charge) baseline values of the mutual capacitances C_(M)(r,s) whenthe touch from the operator is not present in the row scanning mode ofoperation. In an exemplary embodiment, these baseline values of themutual capacitances C_(M)(r,s) are related to a characteristic of designand/or construction of the touchscreen 400.

Ideally, the baseline values of the mutual capacitances C_(M)(r,s) aresubstantially uniform throughout the touchscreen 400, such that localelectrostatic field configurations associated with the capacitivecoupling of the one or more measurement signals between a horizontalelectrode and a vertical electrode are substantially repeatablethroughout the touchscreen 400. In practice, however, differences inconfiguration and arrangements of the vertical electrodes 202.1 through202.k and/or of the horizontal electrodes 302.1 through 302.p can causethe baseline values of the mutual capacitances C_(M)(r,s) to differ.These differences in configuration and arrangement are especiallyprevalent around a perimeter, or edge, of the touchscreen 400, wherebyinterior mutual capacitances differ from edge mutual capacitances. As aresult of these differences between edge mutual capacitances and theinterior mutual capacitances, the baseline values of the edge mutualcapacitances differ from the baseline values of the interior mutualcapacitances.

Herein, mutual capacitances from among the mutual capacitancesC_(M)(r,s) may be described as being an “interior” mutual capacitance if1<r<k and 1<s<p and/or may be described as being an “edge” mutualcapacitance if r=1, r=k, s=1, or s=p. During operation of thetouchscreen 400, the touch of the operator induces changes, ΔC_(M)(r,s),in one or more of the mutual capacitances C_(M)(r,s) that can bemeasured by the associated electronics. In another exemplary embodiment,a ratio between the changes ΔC_(M)(r,s) in one or more of the mutualcapacitances C_(M)(r,s) and their corresponding baseline values, namelythe ratio: ΔC_(M)(r,s)/C_(M)(r,s), should be large and/or the baselinevalues of the mutual capacitances C_(M)(r,s) be substantially uniform.

By way of illustration, FIG. 7A considers the specific case of aninterior mutual capacitance C_(M)(r,s) where r=k−1 and s=2. Thisinterior mutual capacitance C_(M)(k−1,2) corresponds to verticalelectrode 202.k−1 and horizontal electrode 302.2. When associatedelectronics drives horizontal electrode 302.2 with a voltage V, andsensing electronics has measured from vertical electrode 202.k−1 anintegrated signal corresponding to a charge Q, the basic formula thatdefines capacitance, namely Q=CV, results in the measured value ofmutual capacitance C_(M)(k−1,2) being equal to Q/V. During thismeasurement process, all vertical electrodes 202.1 through 202.k andhorizontal electrodes 302.1 through 302.p are grounded or virtuallygrounded, with the exception of the driven horizontal electrode 302.2.

Associated with this measured mutual capacitance C_(M)(k−1,2) is acomplex electrostatic field pattern. Electric field lines that connectdriven horizontal electrode 302.2 to vertical electrode 202.k−1contribute to the value of the mutual capacitance C_(M)(k−1,2) and arerepresented by sixteen short solid heavy lines in FIG. 7A, where fourcross from electrode pad 306.2.q−1 to electrode pad 206.1.k−1, fourcross from electrode pad 306.2.q−1 to electrode pad 206.2.k−1, fourcross from electrode pad 306.2.q to electrode pad 206.1.k−1, and fourcross from electrode pad 306.2.q to electrode pad 206.2.k−1. Additionalelectric field lines, drawn as dotted lines in FIG. 7A, connect thedriven horizontal electrode 302.2 with other electrodes besides verticalelectrode 202.k−1. These additional electric field lines do notcontribute to the value of the interior mutual capacitance C_(M)(k−1,2).As is understood by paraphrasing rigorous electrostatics theory, thenumerical value of mutual capacitance, C_(M)(k−1,2), is proportional toa number of electric field lines connecting horizontal electrode 302.2and vertical electrode 202.k−1, and electrostatic fields, as representedby such patterns of electric field lines, determine the values of mutualcapacitances C_(M)(r,s), such as mutual capacitance C_(M)(k−1,2).

The complex electric field line patterns associated with interior mutualcapacitances tend to be very similar, since associated local electrodegeometries are very similar. Correspondingly, the values of interiormutual capacitances C_(M)(r,s) also tend to be very similar. However,for edge mutual capacitances, differences in local electrode geometry,and hence differences in electric field line patterns, may result insignificant differences in values of mutual capacitance C_(M)(r,s). Thisis illustrated in FIG. 7B which considers the edge mutual capacitanceC_(M)(k,2) associated with horizontal electrode 302.2 and verticalelectrode 202.k.

As illustrated in FIG. 7B, there are four electric field lines betweenelectrode pads 306.2.q and 206.1.k, because the local electrode geometryat the boundary between electrode pads 306.2.q and 206.1.k is the sameas between electrode pads 306.2.q−1 and 206.1.k−1. For similar reasons,there are four electric field lines between electrode pads 306.2.q and206.2.k. In contrast, there are not four electric field lines betweenelectrode pad 206.1.k and electrode terminus 308.2.2 or betweenelectrode pad 206.2.k and electrode terminus 308.2.2 in order to reflecta difference in geometry between electrode terminuses and electrodepads.

With the number of electric field lines associated with edge mutualcapacitance C_(M)(k,2) exceeding the number of electric field linesassociated with interior mutual capacitance C_(M)(k−1,2), the value ofedge mutual capacitance C_(M)(k,2) exceeds the value of interior mutualcapacitance C_(M)(k−1,2). Variations in edge mutual capacitance valuesmay be due to a number of factors such as the geometry of electrodeterminuses, as well as other objects, such as interconnect traces,affecting the local electrostatic environment.

With recognition that the greatest design-inherent variations in mutualcapacitance C_(M)(r,s) values tend to be due to edge mutualcapacitances, there is a need for a design approach that can tune edgemutual capacitance values. Several such approaches are described furtherbelow with respect to FIGS. 9, 10, 11, 12, 13A and 13B. These approachesas further described below rely on having an edge pattern element aspart of the electrode patterns disposed on the one or more substratesforming the touchscreen. In an embodiment, the edge pattern element mayinclude a grounded electrode adjacent to an electrode terminus of afirst electrode for adjusting an edge mutual capacitance between thefirst electrode and a second electrode. The grounded electrode may begrounded using capacitive coupling or using interconnect traces. Inanother embodiment, the grounded electrode may be configured to extendinto a region occupied by a floating island while maintaining a gap withthe floating island. The location of the gap may be configured accordingto a desired edge mutual capacitance value. Alternatively oradditionally, the edge pattern element may be such that the secondelectrode includes a conductive extension configured to increase theedge mutual capacitance between the first electrode and the secondelectrode. In another embodiment, the edge pattern element may includefloating islands having non-uniform widths such that the edge mutualcapacitance between the first electrode and the second electrode isincreased or decreased.

Using a simplified model of a three conductor system having a mutualcapacitance to better describe physics concepts of these approaches,FIGS. 8A, 8B, and 8C illustrate the principal that changes in electrodegeometry may change electrostatic field patterns and hence change mutualcapacitance values.

Referring now to FIG. 8A, a three-conductor system 832 is shown andincludes a driven electrode 822, a primary grounded electrode 824 and asecondary grounded electrode 828. Of interest is the mutual capacitancebetween driven electrode 822 and primary grounded electrode 824. At abasic physics level, the value of mutual capacitance C_(M) is determinedby the electrostatic field that forms around the electrodes when avoltage is applied to driven electrode 822. If driven electrode 822 isdriven with a voltage V, a charge Q will flow away from primary groundedelectrode 824 leaving the opposite change −Q on primary groundedelectrode 824. The charge Q may be measured by current or charge sensingelectronics electrically connected to primary grounded electrode 824resulting in a measured mutual capacitance C_(M)=Q/V. For a givenelectrode geometry, C_(M) may be numerically determined by usingLaplace's Equations to solve for the electrostatic field configuration,as is well appreciated by those of skill in the art. The value of Q, andhence the value of mutual capacitance C_(M), is proportional to thenumber of electric field lines connecting the driven electrode 822 tothe primary grounded electrode 824. With acknowledgment to the 19^(th)century discovery of Michael Faraday regarding the concept that electricfield lines provide an excellent intuitive basis for visuallyconsidering electrostatic fields, electric field lines are schematicallydrawn in FIG. 8A to represent the electrostatic field in the region 830.

Referring now to FIG. 8B, an electrostatic field in region 840 ischanged relative to the electrostatic field in region 830 ofthree-conductor system 832. The change reflects a shift in an upwarddirection 834 of secondary grounded electrode 848, as compared to thesecondary grounded electrode 828 of three-conductor system 832. As aresult, the value of mutual capacitance is larger for thethree-conductor system 842 than for three-conductor system 832, as isimplied by an increased number of electric field lines betweenelectrodes 822 and 824.

Correspondingly, FIG. 8C illustrates a three-conductor system 852 inwhich the secondary grounded electrode 858 is moved in a downwarddirection 836, thus altering the electrostatic fields in region 850 in away that reduces the mutual capacitance between electrodes 822 and 824.

As may not be readily recognized for a touchscreen 400 with its largenumber of (k+p) electrodes, when considering the measurement of oneindividual mutual capacitance value, such as the measurement of mutualcapacitance C_(M)(k,2) highlighted in FIG. 7B, touchscreen 400approximates a three conductor system as described with the conceptualmodels of FIGS. 8A, 8B and 8C. For example, horizontal electrode 302.2of touchscreen 400 is analogous to driven electrode 822 and verticalelectrode 202.k is analogous to primary grounded electrode 824. Becausethe remaining (k+p−2) electrodes of touchscreen 400 are all grounded orvirtually grounded during the measurement of C_(M)(k,2), this entire setof (k+p−2) electrodes of touchscreen 400, as well as any associatedinterconnect and shield traces, may all be considered to be representedby the secondary grounded electrode 828, 848 or 858 of three-conductorsystem 832, 842, or 852. Readers with a deep knowledge of electrostaticswill recognize that for conceptual clarity, if not numerical accuracy,the electric field lines drawn in a very stylized and schematic way inthe figures. Nevertheless, the conclusions drawn from the stylizedelectric field lines are true to the underlying physics ofelectrostatics.

Fourth Exemplary Touchscreen

FIG. 9 illustrates in part a touchscreen 900 that has many elements incommon with touchscreen 400 illustrated in FIGS. 2, 3, 4, 7A and 7Babove. Specifically, touchscreen 900 includes vertical electrodes 202.1through 202.k on substrate 204 and horizontal electrodes 302.1 through302.p on substrate 304. Touchscreen 900 also includes interconnecttraces 910 which make electrical connections between electrodes andassociated electrodes, and are explicitly shown in FIG. 9 for horizontalelectrodes 302.1 and 302.2. It is noted that touchscreen 400 alsoincludes interconnect traces such as interconnect traces 910, even ifnot explicitly shown in FIG. 4A for ease of presentation. For thepurposes of reducing values of edge mutual capacitance C_(M)(k,2),touchscreen 900 also includes grounded electrodes 920.1 and 920.2 on thesurface of substrate 204. Interconnect traces 910 shown in FIG. 9 are onthe surface of the other substrate (substrate 304), which is belowsubstrate 204, and so electrodes 920.1 and 920.2 pass over interconnecttraces 910 with no mechanical interference. Additional interconnecttraces (not shown) on the surface of substrate 204 ground the groundedelectrodes 920.1 and 920.2. Some electric field lines that otherwisewould have gone between terminus 308.2.2 and vertical electrode 202.know go between terminus 308.2.2 and grounded electrodes 920.1 and 920.2,thus reducing the value of C_(M)(k,2). In this manner the additionalgrounded electrodes enable adjustment of edge mutual capacitance values.

The amount of reduction of edge mutual capacitance C_(M)(k,2) isdetermined by how closely grounded electrodes 920.1 and 920.2 encroachvertical electrode 202.k. The corresponding gap distances provide adesign approach to tune the value of C_(M)(k,2). Similarly groundedelectrodes 920.3 through 920.p (not shown) provide an approach to tunethe values of remaining right side edge mutual capacitances C_(M)(k,s)for s=3 to p. Additional grounded electrodes 930 are optionally added atthe corners to provide more ability to tune the corner mutualcapacitances C_(M)(k,1) and C_(M)(k,p). With up to p+2 added groundedelectrodes and associated adjustable gaps, there are sufficient designdegrees of freedom to individually tune all edge mutual capacitancevalues C_(M)(k,s) along the right edge of touchscreen 900. Similardesign principles may be applied to adjust edge mutual capacitances onthe other sides of touchscreen 900.

While touchscreen 900 includes floating islands 212 and 312, it will beapparent to those skilled in the art that the presented approaches fortuning edge mutual capacitances using additional grounded electrodes areequally applicable in touchscreen designs without floating islands 212and 312.

Fifth Exemplary Touchscreen

Touchscreen 1000 shown in part in FIG. 10 illustrates another approachto adjust edge mutual capacitance values. Floating islands 1020 and 1030proximate to horizontal electrode terminuses 1008.1.2 through 1008.p.2are similar to floating islands 212 and floating islands 312respectively, except for a difference in floating island width. Thewidths of floating islands 1020 and 1030 of touchscreen 1000 may beeither greater than or less than the widths of floating islands 212 and312 located elsewhere in touchscreen 1000. Due to differences inadjacent floating island widths, the geometry of the right-most verticalelectrode 1002.k may differ in detail from the geometry of verticalelectrode 202.k of touchscreen 400. As drawn, FIG. 10 illustrates thecase where floating islands 1020 and 1030 are wider than floatingislands 212 and 312, and hence a greater distance of separation betweenhorizontal electrode terminus 1008.2.2 and proximate edges of verticalelectrode 1002.k. This greater distance weakens the correspondingelectric field strength. In FIG. 10, this is represented by fewerelectric field lines being drawn between horizontal electrode terminus1008.2.2 and vertical electrode 1002.k than are drawn between horizontalelectrode terminus 308.2.2 and vertical electrode 202.k in FIG. 7B.

Increasing the widths of floating islands 1020 and 1030 reduces thevalue of edge mutual capacitance C_(M)(k,2). In contrast, decreasing thewidths of floating islands 1020 and 1030 increases the value of edgemutual capacitance C_(M)(k,2). Hence, to the extent that themanufacturing process supports narrower floating island widths, the edgemutual capacitance tuning method illustrated in FIG. 10 enables tuningof edge mutual capacitance values in either direction. Furthermore, notall floating islands 1020 and 1030 need have the same width, thusproviding an approach to individually tune different edge mutualcapacitances.

In alternate embodiments, floating islands 212, 312, 1020 and 1030 maybe removed while retaining the same gaps between vertical and horizontalelectrodes. In such embodiments the same edge capacitance tuning methodapplies with only a shift in attention from island widths to widths ofunfilled gaps between electrodes.

Sixth Exemplary Touchscreen

For cases where it is desirable to increase (not reduce) edge mutualcapacitance values, the example of touchscreen 1100 illustrated in partin FIG. 11 is provided. As illustrated in FIG. 11, vertical electrode1102.k differs from the design of vertical electrode 202.k oftouchscreen 400, such that conductive extensions 1110 are added to theright sides of electrode pads 1106.1.k through 1106.i.k (1106.1.k and1106.2.k explicitly shown in FIG. 11) of vertical electrode 1102.k.Electric field lines between horizontal electrode terminus 308.2.2 andextensions 1110 of vertical electrode 1102.k increase the value ofmutual capacitance C_(M)(k,2). As the size of the extension increases,there is a corresponding increase in mutual capacitance, so the size ofeach extension 1110 provides a way to tune mutual capacitance valuesindividually. Optionally, the terminuses of vertical electrode 1102.kmay include extensions 1120 in order to further enable tuning of cornermutual capacitance values C_(M)(k,1) and C_(M)(k,p). Following the sameprinciples illustrated in FIG. 11, edge mutual capacitances can beadjusted on any side of touchscreen 1100.

While touchscreen 1100 includes floating islands 212 and 312, it will beapparent to those skilled in the art that the presented method fortuning edge mutual capacitances using electrode pad extensions isequally applicable in touchscreen designs without floating islands 212and 312.

Seventh Exemplary Touchscreen

Touchscreen 1200 shown in part in FIG. 12 illustrates yet anotherapproach to edge mutual capacitance tuning based on modifying geometryof electrode terminuses. For example, the geometry of electrode terminus1208.2.2 differs from that of electrode terminus 308.2.2 of touchscreen400. For ease of comparison, dotted outline 1210 shows the geometry ofunmodified electrode terminus 308.2.2. Because of the reduced area ofelectrode terminus 1208.2.2, the terminus has reduced perimeter lengthproximate to electrode 202.k, and hence fewer electric field linesbetween electrode terminus 1208.2 and vertical electrode 202.k. Theresult is a reduced value of mutual capacitance C_(M)(k,2). The shapesof different terminuses may be modified by different amounts. With suchmodifications to the shapes of electrode terminuses 1208.1.2 through1208.p.2, each of the individual values of edge mutual capacitancesC_(M)(k,s) for s=1 to p can be independently tuned. Edge mutualcapacitances on other sides of touchscreen 1200 may be similarlyselectively tuned.

While touchscreen 1200 includes floating islands 212 and 312, it will beapparent to those skilled in the art that the presented method fortuning of edge mutual capacitances using electrode pad extensions isequally applicable in touchscreen designs without floating islands 212and 312.

Eighth Exemplary Touchscreen

Touchscreen 1300 shown in part in FIG. 13A illustrates anotherparticularly advantageous approach for tuning edge mutual capacitances.Just as touchscreen 900 includes grounded electrodes 920, touchscreen1300 includes grounded electrodes 1320. Grounded electrodes 1320 aregrounded via grounded interconnect traces (not shown). However, unlikegrounded electrodes 920, grounded electrodes 1320 extend partially orfully into regions that in touchscreens 400 and 900 are occupied byfloating islands 212.1 and 212.2. If the extensions of groundedelectrodes 1320 do not fully extend into the regions corresponding tothe floating islands 212, the shortened floating islands 1322, and agap, fill the remaining region of floating islands 212. The amount ofreduction of the value of the edge mutual capacitances depends on thelocation of the gap between grounded electrodes 1320 and floatingislands 1322. The further to the left direction that these gaps aremoved, the more that the right edge mutual capacitances are reduced.Furthermore, the amount of reduction will be an approximately linearfunction of the distance these gaps are moved, thus simplifying thetuning processes. Particular advantages result, as described for thedesign of touchscreen 1300.

When, as with the grounded electrodes 920 of touchscreen 900, thegrounded electrodes 1320 of touchscreen 1300 are on a different glasssurface than interconnect traces 910, mechanical interference betweengrounded electrodes 1320 and interconnection traces 910 are avoided.However, as presented with reference to FIG. 13B, it is not arequirement that grounded electrodes be on a different glass surfacethan the interconnect traces.

Touchscreen 1302 of FIG. 13B has grounded electrodes 1330 and floatingislands 1332 that are analogous to grounded electrodes 1320 and floatingislands 1322 of touchscreen 1300 of FIG. 13A. Again right edge mutualcapacitances vary approximately linearly with the location of the gapbetween grounded electrodes 1330 and floating islands 1332. However,unlike for touchscreen 1300, grounded electrodes 1330 and floatingislands are on the same surface of substrate 304 as the horizontalelectrodes 302 and interconnect traces 910. While seemingly impossibleto make the electrical connections necessary to ground the electrodes1330 on the surface of substrate 304, as there is no way to make adirect-current (DC) electrical connection to the electrodes 1330 withoutinterfering with interconnection traces 910, an important insight isthat a direct-current electrical connection is not required and insteadcapacitive coupling may be used.

As shown, touchscreen 1302 includes other grounded electrodes 1334. Inthe plan view of FIG. 13B, grounded electrode 1330 and groundedelectrode 1334 overlap within an overlap area 1336. With A being thearea of overlap area 1336, and symbols d and ε used to represent thethickness and dielectric constant of the optically clear adhesive 408(see FIG. 4B), respectively, then the parallel-plate-capacitor formula,C=εA/d, predicts a capacitive coupling between grounded electrode 1330and grounded electrode 1334. For example, if A=6 mm², d=200 μm, andε=4×8.85 pF/m (picoFarad per meter), then C≈1 pF. As long as thecapacitance between electrodes 1330 and other conductors (not includingthe grounded electrode 1334) is comparable or less than this value, thenelectrodes 1330 will effectively be grounded and serve the intendedpurpose. To compensate for the effects of a lack of a true DC groundconnection, it may be necessary to move the gaps between groundedelectrode 1330 and floating islands 1332 further to the left directionthan would otherwise be necessary, and is readily achievable while roomexists to move the gaps to the left.

As described with reference to FIG. 13A and FIG. 13B, adjustments toedge mutual capacitances on the right side of the touchscreen result. Ofcourse, the illustrated design approaches may be applied to left, topand bottom sides of the touchscreen as well. Furthermore, bothapproaches may be used in the same touchscreen. For example, if it isdeemed desirable to place all grounded electrodes on the lower substrate304, then the design approach of FIG. 13A may be used on the top andbottom sides while the design approach of FIG. 13B may be used on theleft and right sides of the touchscreen. This is of interest because,for cosmetic reasons, the design and manufacture of the user-facing topsubstrate 204 is more constrained than for the bottom substrate 304, asis well appreciated by those skilled in the art.

Of note, the designs of FIGS. 13A and 13B make use of floating islands212 and 312, and modifications thereof to simultaneously provide fortouchscreens with electrode patterns of low visibility, having adjustededge mutual capacitance values, while being compatible with screenprinting manufacturing processes.

Of further note, the ability to tune edge mutual capacitance to ensurethat none of the values of edge mutual capacitances significantly exceedthe values of interior mutual capacitances avoids loss of effectiveanalog-to-digital-convertor (ADC) resolution when measuring C_(M)(r,s).Often, in the measurement of all mutual capacitance values C_(M)(r,s),the same electronics gain is used. With the understanding that touchesreduce, rather than increase, measured mutual capacitance values, andthus, touch induced changes to mutual capacitance values have suchlittle effect on gain settings, prevention of ADC full-scale saturationfor any of the mutual capacitance measurements focuses on electronicsgain being determined by the maximum mutual capacitance C_(M)(r,s)value. With substantially minimized variation, effective ADC resolutionfor mutual capacitance measurements can be achieved.

Of additional note, the ability to tune edge mutual capacitance hasfurther potential positive impact. On a touchscreen production line, themeasured variance of C_(M)(r,s) values provides a convenient qualitytest. However, any such measured mutual-capacitance variance includesnot only possible effects of manufacturing variations, but alsomutual-capacitance variations inherent in the product design. As can bewell appreciated, improvements to minimize variations in the productdesign allow production line quality testing based on measured varianceof C_(M)(r,s) values to be more sensitive to the production floorquality itself.

Exemplary Fabrication Techniques that can be Used to Fabricate theExemplary Touchscreens According to an Exemplary Embodiment of thePresent Disclosure

FIG. 14 is a flowchart of a first exemplary fabrication control flowthat can be used to fabricate the touchscreens according to an exemplaryembodiment of the present disclosure. The disclosure is not limited tothis exemplary fabrication control flow. Rather, it will be apparent topersons skilled in the relevant art(s) that other fabrication controlflows are within the scope and spirit of the present disclosure. Thefollowing discussion describes a fabrication control flow 1400 of atouchscreen, such as the touchscreen 102, the touchscreen 400, thetouchscreen 520, the touchscreen 622, the touchscreen 900, thetouchscreen 1000, the touchscreen 1110, the touchscreen 1210, thetouchscreen 1300 and/or the touchscreen 1302 to provide some examples,and represents a single transparent conductive material design, such asthe SITO design as described in FIG. 1, having two transparentsubstrates, each of the transparent substrates having a correspondingelectrode pattern.

At step 1402, deposition of transparent conductive material onto a firsttransparent substrate occurs, such as the transparent substrate 204. Inan exemplary embodiment, the transparent substrate is implemented usinga plate of glass and the transparent conductive material is indium tinoxide (ITO).

At step 1404, selective patterning of the first transparent substrateoccurs to form a first electrode pattern, such as the first electrodepattern 200, the first electrode pattern 500, and/or the first electrodepattern 600. In an exemplary embodiment, a screen printing process isused to deposit an etchant material onto the first transparent substrateof step 1402 using a mask, the mask having the negative of a pattern ofthe first electrode pattern, and an etching process, such as a wet ordry etch, patterns the first transparent substrate of step 1402 to formthe first electrode pattern. The etching process removes any conductivematerial from the first transparent substrate of step 1402 that is notcovered by the mask while leaving any conductive material from the firsttransparent substrate of step 1402 that is covered by the mask.

At step 1406 deposition of transparent conductive material onto a secondtransparent substrate, such as the transparent substrate 304, occurs.The transparent conductive material options for step 1406 are the sameas for step 1402.

At step 1408, selective patterning of the second transparent substrateof step 1406 occurs to form a second electrode pattern, such as thesecond electrode pattern 300, the second electrode pattern 510, and/orthe second electrode pattern 612. In an exemplary embodiment, thefabrication control flow 1400 uses a screen printing process similar tothat in step 1404.

At step 1410, the first pattern transparent substrate of step 1404 andthe second pattern transparent substrate of step 1408 are attached toeach other with an optically clear adhesive (OCA) to form thetouchscreen. The OCA can be an acrylic-based adhesive, a silicone-basedadhesive, polyvinyl butyral (PVB), ethylene-vinyl acetate (EVA), or anyother suitable OCA that will be recognized by those skilled in therelevant art(s) without departing from the spirit and scope of thepresent disclosure.

FIG. 15 is a flowchart of a second exemplary fabrication control flowthat can be used to fabricate the touchscreens according to an exemplaryembodiment of the present disclosure. The disclosure is not limited tothis exemplary fabrication control flow. Rather, it will be apparent topersons skilled in the relevant art(s) that other a fabrication controlflows are within the scope and spirit of the present disclosure. Thefollowing discussion describes a fabrication control flow 1500 of atouchscreen, such as the touchscreen 102, the touchscreen 400, thetouchscreen 520, the touchscreen 622, the touchscreen 900, thetouchscreen 1000, the touchscreen 1110, the touchscreen 1210, thetouchscreen 1300 and/or the touchscreen 1302. The fabrication controlflow 1500 of FIG. 15 represents a double transparent conductive materialdesign, such as the DITO design as described in FIG. 1, having onetransparent substrate with two electrode patterns.

At step 1502, transparent conductive material deposition onto a firstside and a second side of a first transparent substrate, such astransparent substrate 304 for example, occurs. In an exemplaryembodiment, the transparent substrate is implemented using a plate ofglass.

At step 1504, selectively patterning the first side of the firsttransparent substrate of step 1502 occurs to form a first electrodepattern, such as the first electrode pattern 200, the first electrodepattern 500, and/or the first electrode pattern 600. In an exemplaryembodiment, a screen printing process is used to deposit an etchant,having a negative of the pattern of the first electrode pattern, ontothe first transparent substrate of step 1502, and an etching process,such as a wet or dry etch, is used on the first side of the firsttransparent substrate of step 1502 to form the first electrode pattern.The etching process removes any conductive material from the first sideof the first transparent substrate of step 1502 that is not covered bythe mask while leaving any conductive material from the first side ofthe first transparent substrate of step 1502 that is covered by themask.

At step 1506, selectively patterning of the second side of the firsttransparent substrate of step 1502 occurs to form a second electrodepattern, such as the second electrode pattern 300, the second electrodepattern 510, and/or the second electrode pattern 612. In an exemplaryembodiment, a screen printing process is used to deposit an etchant,having a negative of the pattern of the second electrode pattern, ontothe second transparent substrate of step 1504, an etching process, suchas a wet or dry etch, is used to pattern the second side of the firsttransparent substrate of step 1502 to form the second electrode pattern.The etching process removes any conductive material from the second sideof the first transparent substrate of step 1502 that is not covered bythe mask while leaving any conductive material from the second side ofthe first transparent substrate of step 1502 that is covered by themask.

At step 1506, the first pattern transparent substrate of step 1504 and asecond pattern transparent substrate are attached to each other with anoptically clear adhesive (OCA) to form the touchscreen.

Conclusion

The Detailed Description referred to accompanying figures to illustrateexemplary embodiments consistent with the disclosure. References in thedisclosure to “an exemplary embodiment” indicates that the exemplaryembodiment described include a particular feature, structure, orcharacteristic, but every exemplary embodiment can not necessarilyinclude the particular feature, structure, or characteristic. Moreover,such phrases are not necessarily referring to the same exemplaryembodiment. Further, any feature, structure, or characteristic describedin connection with an exemplary embodiment can be included,independently or in any combination, with features, structures, orcharacteristics of other exemplary embodiments whether or not explicitlydescribed.

The exemplary embodiments described within the disclosure have beenprovided for illustrative purposes, and are not intend to be limiting.Other exemplary embodiments are possible, and modifications can be madeto the exemplary embodiments while remaining within the spirit and scopeof the disclosure. The disclosure has been described with the aid offunctional building blocks illustrating the implementation of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed.

The Detailed Description of the exemplary embodiments fully revealed thegeneral nature of the disclosure that others can, by applying knowledgeof those skilled in relevant art(s), readily modify and/or adapt forvarious applications such exemplary embodiments, without undueexperimentation, without departing from the spirit and scope of thedisclosure. Therefore, such adaptations and modifications are intendedto be within the meaning and plurality of equivalents of the exemplaryembodiments based on the teaching and guidance presented herein. It isto be understood that the phraseology or terminology herein is for thepurpose of description and not of limitation, such that the terminologyor phraseology of the present specification is to be interpreted bythose skilled in relevant art(s) in light of the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. For example, asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” and “including,” when used herein, specify thepresence of stated features, steps, operations, elements, andcomponents, but do not preclude the presence or addition of one or moreother features, steps, operations, elements, components, or groupsthereof.

What is claimed is:
 1. A touchscreen, comprising: a transparentsubstrate; a first layer of electrode patterns disposed on thetransparent substrate, the first layer of electrode patterns comprising:a first electrode and a first floating transparent conductive islandadjacent to the first electrode, an electrode terminus of a thirdelectrode, and a third floating transparent conductive island adjacentto the electrode terminus; and a second layer of electrode patternscomprising a second electrode and a second floating transparentconductive island adjacent to the second electrode, wherein the secondfloating transparent conductive island overlaps the electrode terminusand the third floating transparent conductive island.
 2. The touchscreenof claim 1, wherein the first layer and the second layer of electrodepatterns avoid a high-contrast discontinuity by providing a perceivedlayer of transparent conductive material.
 3. The touchscreen of claim 1,further comprising an edge pattern element configured to adjust an edgemutual capacitance between the electrode terminus and the secondelectrode.
 4. The touchscreen of claim 3, wherein the edge patternelement comprises a grounded electrode adjacent to an edge boundary ofthe electrode terminus.
 5. The touchscreen of claim 4, wherein thegrounded electrode is grounded via capacitive coupling to a secondgrounded electrode.
 6. The touchscreen of claim 4, wherein the groundedelectrode is electrically connected to ground without capacitivecoupling.
 7. The touchscreen of claim 4, further comprising interconnecttraces for grounding the grounded electrode.
 8. The touchscreen of claim3, wherein the first electrode further comprises an electrode pad and asecond electrode terminus adjacent to the electrode pad, wherein theedge pattern element creates a greater separation distance between thesecond electrode and the second electrode terminus than between thesecond electrode and the electrode pad.
 9. The touchscreen of claim 3,wherein the edge pattern element comprises a conductive extension to thesecond electrode, and wherein the conductive extension is configured toadjust the edge mutual capacitance between the first electrode and thesecond electrode. The touchscreen of claim 1, wherein the third floatingtransparent conductive island is configured to adjust an edge mutualcapacitance between the electrode terminus and the second electrode. 11.A method for fabricating a touchscreen, comprising: disposing on a firsttransparent substrate a first pattern comprising: a first electrode, afirst floating transparent conductive island adjacent to the firstelectrode, an electrode terminus of a third electrode, and a thirdfloating transparent conductive island adjacent to the electrodeterminus; and disposing on a second transparent substrate a secondpattern comprising: a second electrode, and a second floatingtransparent conductive island located adjacent to the second electrode,wherein the second floating transparent conductive island overlaps theelectrode terminus and the third floating transparent conductive island.12. The method of claim 11, wherein the first layer and the second layerof electrode patterns avoid a high-contrast discontinuity by providing aperceived layer of transparent conductive material when viewed from anangular direction.
 13. The method of claim 11, further comprising anedge pattern element configured to adjust an edge mutual capacitancebetween the electrode terminus and the second electrode.
 14. The methodof claim 13, wherein the edge pattern element comprises a groundedelectrode adjacent to an edge boundary of the electrode terminus. 15.The method of claim 14, wherein the grounded electrode is grounded viacapacitive coupling to a second grounded electrode.
 16. The method ofclaim 14, wherein the grounded electrode is electrically connected toground without capacitive coupling.
 17. The method of claim 14, furthercomprising interconnect traces for grounding the grounded electrode. 18.The method of claim 13, wherein the first electrode further comprises anelectrode pad and a second electrode terminus adjacent to the electrodepad, wherein the edge pattern element creates a greater separationdistance between the second electrode and the second electrode terminusthan between the second electrode and the electrode pad.
 19. The methodof claim 13, wherein the edge pattern element comprises a conductiveextension to the second electrode, and wherein the conductive extensionis configured to adjust the edge mutual capacitance between the firstelectrode and the second electrode.
 20. The method of claim 11, whereinthe third floating transparent conductive island is configured to adjustan edge mutual capacitance between the electrode terminus and the secondelectrode.